CVE-2021-47577: io-wq: check for wq exit after adding new worker task_work

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-06-19 · updated 2026-08-04
Weakness: CWE-362

Description

In the Linux kernel, the following vulnerability has been resolved: io-wq: check for wq exit after adding new worker task_work We check IO_WQ_BIT_EXIT before attempting to create a new worker, and wq exit cancels pending work if we have any. But it's possible to have a race between the two, where creation checks exit finding it not set, but we're in the process of exiting. The exit side will cancel pending creation task_work, but there's a gap where we add task_work after we've canceled existing creations at exit time. Fix this by checking the EXIT bit post adding the creation task_work. If it's set, run the same cancelation that exit does.

Affected products

Linux kernel: before 5.15.11; 5.16-rc1, 5.16-rc2, 5.16-rc3, 5.16-rc4 — fixed in 5.15.11

How to fix

Upgrade to a fixed version: Linux kernel 5.15.11. Check the vendor advisory for mitigations.

References

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